Locality of quark-hadron duality and deviations from quark counting rules above resonance region

Abstract

We show how deviations from the dimensional scaling laws for exclusive processes may be related to a breakdown in the locality of quark-hadron duality. The essential principles are illustrated in a pedagogic model of a composite system with two spinless charged constituents, for which a dual picture for the low-energy resonance phenomena and high-energy scaling behavior can be established. We introduce the concept of "restricted locality" of quark-hadron duality and show how this results in deviations from the pQCD quark counting rules above the resonance region. In particular it can be a possible source for oscillations about the smooth quark counting rule, as seen e.g. in the 90-degree differential cross sections for $\gamma p\to {\pi }^{+}n$.

Comments: The way to present Eqs. (2), (4), (7) are changed while physics contents and calculations are left intact; Additional explanations for the forward and large-angle duality are added; Three more references are included; Version to appear on Phys. Rev. Lett